The present invention relates to an electrophotographic processor, such as a laser beam printer, a xerographic copier, a facsimile unit, etc., and more particularly, to a system for maintaining a uniform spacial gap between a developing roller and a doctor blade in an electrophotographic processor without using a thickness gauge.
In an electrophotographic image forming process, toner is charged and brought into contact with the surface of a rotating developing roller which carries the toner into contact with a photoconductive drum. The developing roller is semiconductive and charged to a potential between that on the toner and that on charged areas of the photoconductive drum. As the developing roller rotates, toner is attracted to an outer surface of the developing roller from a supply source of the toner.
When the developing roller surface has left contact with the toner supply and is rotating towards a nip contact with the surface of the photoconductive drum, it encounters a doctor blade which limits toner to a controlled, thin layer on the developing roller. U.S. Pat. No. 5,085,171 entitled Compliant Doctor Blade issued to Aulick et al. discloses a conventional design for a developing roller and doctor blade. In Aulick et al. '171, the doctor blade has an outer metal surface on a grit layer with flexible backing. The doctor blade is pushed by foam, or alternatively, by inherent resilience, onto an outer surface of the developing roller. This compliance reduces toner variations which result from surface variations of the doctor blade and the developing roller. While conventional art, such as Aulick et al. '171, provides benefits in its own right, I note that it fails to adequately provide a structure that facilitates assembly while concomitantly maintaining a uniform spacial gap between the doctor blade and the developing roller.